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6174B–ATARM–07-Nov-05
AT91FR40162S Preliminary
Data float wait states do not delay internal memory accesses. Hence, a single access to an
external memory with long t
DF
will not slow down the execution of a program from internal
memory.
The EBI keeps track of the programmed external data float time during internal accesses, to
ensure that the external memory system is not accessed while it is still busy.
Internal memory accesses and consecutive accesses to the same external memory do not have
added Data Float wait states.
Figure 10-14. Data Float Output Time
Notes:
1. Early Read Protocol
2. Standard Read Protocol
10.9.3
External Wait
The NWAIT input can be used to add wait states at any time. NWAIT is active low and is
detected on the rising edge of the clock.
If NWAIT is low at the rising edge of the clock, the EBI adds a wait state and changes neither the
output signals nor its internal counters and state. When NWAIT is de-asserted, the EBI finishes
the access sequence.
The NWAIT signal must meet setup and hold requirements on the rising edge of the clock.
ADDR
NRD
D0 - D15
MCK
t
DF
(1)
(2)
NCS
Содержание AT91FR40162S
Страница 180: ...180 6174B ATARM 07 Nov 05 AT91FR40162S Preliminary Figure 19 2 MCKO Relative to NRST NRST tD MCKO...
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Страница 204: ...204 6174B ATARM 07 Nov 05 AT91FR40162S Preliminary 23 AT91FR40162S Errata There is no known errata for the AT91FR40162S...